Oslo — Negotiators have several terms for the way they plan to enforce any deal reached at global climate talks in Paris this December. "Peer pressure" and "cooperation" are a couple. "Race to the top" is the American buzzword.

What you won't hear mentioned is the word "sanctions." Or "punishment."

For all their efforts to get 200 governments to commit to the toughest possible cuts in greenhouse gas emissions, climate negotiators have all but given up on creating a way to penalize those who fall short.

The overwhelming view of member states, says Christiana Figueres, head of the U.N. Climate Change Secretariat, is that any agreement "has to be much more collaborative than punitive," if it is to happen at all.

"Even if you do have a punitive system, that doesn't guarantee that it is going to be imposed or would lead to any better action," Figueres said.

To critics, the absence of a legal stick to enforce compliance is a deep - if not fatal - flaw in the Paris process, especially after all countries agreed in 2011 that an agreement would have some form of "legal force."

They warn that a deal already built upon sometimes vague promises from member states could end up as a toothless addition to the stack of more than 500 global and regional environmental treaties, while the rise in global temperatures mounts inexorably past a U.N. ceiling of 2 degrees Celsius (3.6 Fahrenheit), with the prospect of ever more floods, droughts and heatwaves.

International Climate Court?

That fear finds its sharpest expression in a proposal from Bolivia's socialist government for an International Climate Justice Tribunal with powers to penalize countries that break commitments.

Diego Pacheco, Bolivia's chief negotiator, said anything less would be "dangerous to Mother Earth."

But the idea is a non-starter with almost every other country going to the Paris talks, from Nov. 30-Dec. 11.

Even the European Union, which has long argued for a strong, legally binding deal, is increasingly talking about a "pledge and review" system under which national commitments would be re-assessed every five years against a goal of halving world emissions by 2050.

Elina Bardram, head of the European Commission delegation, insisted that strong compliance mechanisms were vital. "Weak rules would undermine the whole structure," she said.

However, many developing nations oppose reviews of their goals, wanting oversight to be limited to the rich.

Nick Mabey, chief executive of the E3G think-tank in London, says a Paris deal is likely to be more like international agreements limiting nuclear weapons than accords under the World Trade Organization, which can impose sanctions.

A watchword of nuclear non-proliferation - "trust but verify" - could be the basis, he said.

Yvo de Boer, the United Nations' former top climate official, said he remembers the moment when he realized that the principle of sanctioning countries for non-compliance was dead.

In 2001, as a senior member of the Dutch delegation, de Boer attended a closed-door meeting of environment ministers in Bonn, Germany, that was designing rules to enforce the U.N.'s 1997 Kyoto Protocol, which obliged about 40 rich nations to cut greenhouse gas emissions.

Empty act

He recalled being struck by the strength of objections, even from once-supportive countries such as Australia and Japan, to any attempt to punish those who fell short of emissions commitments.

"The agreement was to be legally binding, but it became very clear that a lot of countries didn't want sanctions," he said.

Despite the opposition, a sanctions regime was agreed later in 2001. It required any developed country that missed its greenhouse gas targets between 2008 and 2012 to make even deeper cuts in the future.

But even those sanctions were an empty act of bravado by rich nations angered by U.S. President George W. Bush's decision in March 2001 to stay out of Kyoto, said Jan Pronk, a former Dutch environment minister who chaired the Bonn meeting.

"There was a political feeling that the United States cannot just kill something that is so important internationally," Pronk recalled. But now that even the flawed Kyoto agreement had expired, he added, "sanctions don't mean anything any more."

He noted that Japan, Russia and Canada - which was set to break its pledge - have simply abandoned Kyoto in recent years, without suffering sanctions.

"Kyoto was the high-water mark for the idea of sanctions in climate agreements," said Alex Hanafi of the U.S. Environmental Defense Fund.

'Race to the top'?

Both China and the United States, the two top carbon emitters crucial to any effective agreement, made clear from the start of the current negotiations they would not agree to any form of international oversight. The U.S. position instead speaks of a collective "race to the top," in which countries push each other to see who can be the greenest.

Nor do the loose commitments being made by countries lend themselves to easy enforcement. Russia's pledge, for example, says only that limiting emissions to somewhere between 70 and 75 percent of 1990 levels by 2030 "might be a long-term indicator."

All countries agree that that the emissions curbs pledged so far are too small to get the world on track to limit warming to 2 degrees Celsius.

That means a strong mechanism will be needed for ratcheting up pledges after Paris.

Critics say that simply shaming outliers will not ensure compliance and that, unless there are costs for non-compliance, any country can share in the global benefits of reduced temperature rises while leaving the hard work of emissions cuts to others.

But Figueres, the U.N. climate chief, believes that cuts in greenhouse gases can serve countries' economic self-interests. China, for instance, can improve the health of millions by shifting from coal-fired power plants that cause air pollution.

And sharp falls in the costs of solar and wind power also mean that greener technologies can help, rather than hinder, economic growth, benefits that were not so evident under Kyoto, she said.

The Paris accord also holds out carrots for participation by developing nations, including a new mechanism to fund loss and damage from hurricanes, droughts or rising sea levels.

De Boer, who now works for the Global Green Growth Institute in South Korea, said that ditching sanctions was, ultimately, part of the price of getting a broad, global agreement.

"The sting has been taken out of the process ... That means the chances of a deal are much better."